High-performance ceramic heat shields are used in many technical applications in order to withstand temperatures between 1000 and 1600 degrees Celsius. In particular the heat shields of turbine machines such as gas turbines and turbine power plants, as used in electricity-generating power stations and in larger aircraft, have correspondingly large surfaces requiring to be shielded off by means of heat shields in the interior of the combustion chambers. Due to the thermal expansion and to large dimensions the shield has to be composed of a plurality of individual heat shield elements manufactured from ceramic material, which elements are spaced apart from one another by a sufficient gap. Said gap provides the heat shield elements with sufficient space to allow for the thermal expansion. However, since the gap also allows direct contact between the hot combustion gases and the supporting structure carrying the heat shield, a cooling fluid in the form of cooling air is injected through the gaps via cooling ducts in the direction of the combustion chamber as an effective countermeasure. Said cooling air is also used in a targeted manner for blasting and hence cooling the metal retaining fixtures by means of which the ceramic heat shield elements (CHS: Ceramic Heat Shields) are clamped to the supporting structure.
In order to implement the retaining fixtures as simply as possible and ideally as a single piece, a method of construction is known in which said retaining fixtures on the one hand can be inserted in an interlocking manner into the installation grooves embodied circumferentially and in parallel in the supporting structure, and on the other hand are clamped by means of embodied gripper sections into the retaining grooves embodied in lateral edges of the ceramic heat shield element. The heat shield elements are inserted one by one by means of the retainers into the grooves of the supporting structure, with the following elements locking the previously positioned elements in their positions. In this way a circumferential row of heat shield elements can be formed for example in a combustion chamber of a gas turbine.
However, the final remaining heat shield element cannot be installed in this way, because the adjacent heat shield elements present on either side prevent a tangentially directed installation movement. A final heat shield element of said type is often referred to as a dummy panel or blank. Consequently, in order to install the final heat shield element use is made of solutions comprising screw connections which enable the heat shield element to be installed in the direction of the surface normals of the supporting structure.
Toward that end a known screw connection uses screws which engage in the recesses embodied for this purpose in lateral edges of the heat shield element. A disadvantage of this solution is that the installation entails a handling problem. For example, the handling of the four screws necessitates the use of fixing means such as bonding or adhesive tape which are not reliable, as a result of which the screws can get lost and absolutely must be found again prior to startup due to the high risk of a turbine being damaged. Furthermore the overhead installation is difficult because the screws can tilt due to the fixing by means of adhesive tape and consequently cannot be introduced into the drilled holes provided. Since the heat shield is the last one to be installed, the screws cannot be positioned by hand, but must be threaded into the holes—without benefit of sight—by means of a hexagon socket screw key.
EP 1 701 095 A1 and EP 0 558 540 B1 describe by way of example a heat shield embodied as cited hereintofore and having the advantages and problems described. The heat shield elements are also referred to among the technical community as bricks and the retaining elements holding them as brick retainers, and the grooves cut out in the lateral edges of the heat shield elements are referred to as pockets.